Water Science & Technology Vol 43 No 7 pp 367–376 © IWA Publishing 2001
A systematic approach to error isolation in computerized wastewater simulation models
JA Lennox*, Z Yuan** and J Harmand***
*
AWMC, Department of Chemical Engineering, The University of Queensland,
St Lucia 4072, QLD, Australia (Tel: +61 7 3365 4374) (Fax: + 61 7 3365 4726)
(E-mail: zhiguo@@awmc.uq.edu.au)
**
AWMC, Department of Chemical Engineering, The University of Queensland,
St Lucia 4072, QLD, Australia (Tel: +61 7 3365 4374) (Fax: + 61 7 3365 4726)
(E-mail: zhiguo@@awmc.uq.edu.au)
***
LBE INRA, Avenue des Etangs, Narbonne 11100, France
ABSTRACT
Activated sludge models are used extensively in the study of wastewater
treatment processes. While various commercial implementations of these
models are available, there are many people who need to code models
themselves using the simulation packages available to them. Quality
assurance of such models is difficult. While benchmarking problems
have been developed and are available, the comparison of simulation
data with that of commercial models leads only to the detection, not
the isolation of errors. To identify the errors in the code is
time-consuming.
In this paper, we address the problem by developing a systematic and
largely automated approach to the isolation of coding errors. There are
three steps: firstly, possible errors are classified according to their
place in the model structure and a feature matrix is established for each
class of errors. Secondly, an observer is designed to generate residuals,
such that each class of errors imposes a subspace, spanned by its feature
matrix, on the residuals. Finally, localising the residuals in a subspace
isolates coding errors. The algorithm proved capable of rapidly and
reliably isolating a variety of single and simultaneous errors in a
case study using the ASM1 activated sludge model. In this paper a newly
coded model was verified against a known implementation. The method is
also applicable to simultaneous verification of any two independent
implementations, hence is useful in commercial model development.
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